This article will turn many people nuts and some would call my theory farfetched but it has happened before and I will try to explain the basis here

Post last radio message “Good Night” #MH370 reaching upto the waypoint #IGARI #MH370 was at the approximate height of 32000ft to 33000ft and it disappeared from the radar control.

and post that there happen two significant incidents and for both of those incidents #First #officer was in the picture.